Many believe Earth may be warming. While much has been made of mankind's contribution to what may be a current global warming trend, it is not certain to what extent mankind may have contributed to global warming. Many if not most approaches discussed in scientific literature to mitigate global warming are reactionary or defensive and revolve around reducing suspected sources of Greenhouse gases. It is entirely possible, however, that global warming would continue even if Greenhouse gases produced by mankind were suspended or eliminated. Regardless, measures that use other approaches may be desirable.